This invention relates to client server computer networks having a plurality of network server computers, and more particularly to a method and apparatus for balancing the load on respective network server computers in the network.
In large client server networks such as the INTERNET, many client computers seek to access the same network server computer at a given time. To do so, each client computer issues an access request which specifies an address for the server computer. When too many clients attempt to access the same server computer at a given time, response time slows as the server handles a queue of requests. To handle the load, it is common for INTERNET service providers to include multiple computers which are linked together to have the same address. For example, a hardware device may respond to all requests to a given address and forward the respective requests to any one of a plurality of redundant network servers. Such hardware device balances the load among the redundant servers allowing response time to be maintained at a desirable speed. Such a hardware device typically handles 16, 64 or 128 servers. To assure that the client is able to access desired data, all accessible data is to be redundantly located on each server computer having the same address. Thus, the multiple servers sharing a common physical address on the client server network are referred to herein as redundant servers.
One shortcoming of this hardware based load balancing approach is that all requests to the server address are routed through a common pipeline (i.e., the hardware load balancing device). Thus, associated with this single point of load balancing control is a single point of failure. In the event of a natural disaster or a prolonged power outage at the hardware load balancing device, client computers are unable to access the desired data at any of the redundant server computers. Accordingly, there is a need for an alternative, more reliable, more flexible technique for achieving load balancing of client demand.